The present invention relates to the manufacture of parts such as metal turbomachine blades, which have internal cavities of complex geometry forming especially cooling circuits, using the technique of lost-wax casting.
The manufacture of such blades involves a pattern made of wax or equivalent material, which comprises an internal part forming a casting core and the configuration of the cavities of the blade. To form the pattern, a wax injection mold is used, in which the core is placed and wax injected into it. The wax pattern is then dipped several times in slips consisting of a suspension of ceramic particles so as to form a shell mold. The wax is removed and the shell mold fired. The blade is obtained by pouring molten metal into the shell, this metal occupying the voids between the inner wall of the shell mold and the core. Thanks to a seed or an appropriate selector and controlled cooling, the metal solidifies in the desired structure. Depending on the nature of the alloy and the expected properties of the part resulting from the casting operation, the alloy may undergo directional solidification giving a columnar structure (DS), directional solidification giving a single-crystal structure (SX) or equiaxed solidification (EX), respectively. The two first families of parts relate to superalloys for parts exposed to high stresses, both thermal and mechanical, in the turbojet, such as the HP turbines' blades.
After the alloy has solidified, the shell and the core are shaken out, giving the desired blade.